1. Field of the Invention
The present invention is generally in the field of semiconductors. More particularly, the invention is in the field of wafer level packaging.
2. Background Art
Electronic devices, such as cellular phones and personal digital assistants (PDAs), continue to decrease in size and price and increase in functionality. As a result, these electronic devices require smaller, lower cost components, such as integrated circuits (ICs) and Micro-Electro-Mechanical Systems (MEMS) devices. However, packaging generally consumes between approximately 40.0 percent and approximately 90.0 percent of the total manufacturing cost of the ICs and MEMS devices. As a result, wafer level packaging has emerged as a leading solution to the challenge of providing low cost IC and MEMS device packages that also have a reduced footprint.
In wafer level packaging processes, a layer of polymer material may be used to bond a cap wafer to a device wafer, which may include ICs or MEMS devices, to reduce cost. However, most polymer based wafer level packages do not provide a hermetic seal, which is required in certain applications. To achieve a hermetic seal, a thin metal layer, such as gold, gold-based alloys, copper, copper-based alloys, or solder, may be used to form a bonding layer to bond the cap wafer to the device wafer. However, the use of the metal bonding layer undesirably increases manufacturing cost.
Additionally, passive components, such as inductors, resistors, and capacitors, are generally required for matching IC and MEMS devices, such as Radio Frequency (RF) IC and RF MEMS devices, in wafer level packages. In one conventional packaging process, the passive components are built in a multi-layer printed circuit board (PCB) substrate and packaged with the wafer level package, which requires the additional cost of another package level to achieve a stand-alone device. In another conventional packaging process, passive components are built on the surface of a PCB, which undesirably consumes additional package space.
Thus, there is a need in the art for a low cost, hermetically sealed wafer level package including a device on a device wafer, where the device can be coupled to a passive component external to the device wafer without undesirably increasing the package footprint.